From: Christina Z. Anderson (zphoto@montana.net)
Date: 02/28/03-11:29:04 AM Z
Hi list,
I'm about finished with my gum research and now going into printing gum
after 4 years hiatus. I wanted to share some research with you guys for
whatever it is worth--maybe nothing.
First of all, I was incorrect with a date in a previous post. Paul
Anderson did NOT write his stain test in 1911, but 1930's as it was in the
Handbook of Photography, Henney and Dudley, in 1938. Demachy's Book Photo
Aquatint is actually co-authored with Maskell and dates 1898. He has the
stain testing in there that I have previously reported.
Who wants to run a quickie test with me with glyoxal?? Please correct
me, scientists: I thought we could paint straight glyoxal on a scrap of
paper in a swath, and then add a bit of sodium carbonate to some glyoxal and
paint a strip of that next to the previous. Then see if there is an
appreciable yellowing going on. Next, you could REALLY rinse out the paper
as best as possible, or use an acid neutral paper, or even acidify a piece
of paper by soaking it in vinegar, and perform the same test. Somehow, I
know there is a way to test this alkaline/glyoxal possibility of staining.
We could take both tests and keep them in the dark, and both and put them in
the sun. Any takers? I do feel the glyoxal yellowing is something important
to test, even though there are so many variables. If the yellowing is
greater where there is more concentrated gelatin at the edge of the paper,
that does not disprove this possibility, but strengthens it. First of all,
more gelatin, more glyoxal in there (if glyoxal is not done in a separate
step). Second of all, more gelatin, less light passes thru, more stain is
noticeable. I AM NOT A SCIENTIST OR AN AUTHORITY SO PLEASE POINT OUT MY
ERRORS! Seriously, what I always miss is the very obvious, right under my
nose.
The research behind my wonderings is that we are told we can speed up
or slow down emulsion sensitivity with ammonia and lemon juice, alkaline and
acid, and with previous research into acids and mordancage, maybe I'm
fixated on this pH thing. But the pH factor IS a factor in gum printing,
and may be in glyoxal staining, paper staining, as well as it does factor
into printing speed.
Second, as far as pigment stain, is it possible (I'm still on this
acid/alkaline wavelength so bear with me) that the more dichromate added to
the sensitizer mixture, the more acid the mixture, and the more the paper
stains because the acid "mordants" the color to the paper, as in dye
mordanting or etching in mordancage? Like when you were a kid and dyed
easter eggs and you used vinegar to "set" the dye? I came up with this idea
as I was cyanotyping in my bathtub, and decided to try some straight
vinegar, and it nicely fixed blue cyano solution ALL over my porcelain tub.
Third, the Melvin methyl alcohol idea has been around quite a while in
an interesting fashion, from E. J. Wall's 1928 Practical Color Photography:
To brush on the sensitizer, he recommends a solution of 30g am di, 15g
citric, and 500ml water with 500 (yes!) ml denatured or methyl alcohol, BUT
this is painted on the BACK of the paper, so go figure. What is up with
that?
Wall also says that spoiled gum arabic may be more liquid but still
does fine.
Fourth, Wall's Photographic Facts and Formulas from 1929, p. 256-7 has
the weirdest formula, and maybe there is something important in here, so I
share it not knowing what the heck it is all about:
"Formula for Pure Whites:
Frequently pure whites are difficult to obtain with this process, and the
following is said to obviate this trouble:
potassium bichromate 72g
water 450 ccm
Dissolve by heat, add enough ammonia to make a solution smell
distinctly, and then heat to drive off excess of ammonia (the "smell" method
of accuracy?!).
Beat the whites of several eggs to a froth, and allow to stand for 24
hr to liquefy. The pigmenting solution is:
450ccm of the bichromate sol, above
cupric sulphate 90g
gum arabic, powdered 800g
pigment 600g
albumen 200ccm
glycerine 100ccm
Mix well and apply as usual to the paper."
I just don't understand what the cupric is doing in there.
Fifth, I noticed that the Part B hardener of Kodak Rapid Fix is
sulfuric acid. Since I don't use the part B in film (I develop in pyro) or
paper (I tone) why couldn't that be used to clear stubborn chromium stain??
My thoughts for the day,
Chris
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